Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-08-05T12:52:39Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Clodoaldo Valverde.pdf: 2861870 bytes, checksum: 93cb3d40f190a12da1c2418490919053 (MD5) / Made available in DSpace on 2014-08-05T12:52:39Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Clodoaldo Valverde.pdf: 2861870 bytes, checksum: 93cb3d40f190a12da1c2418490919053 (MD5) Previous issue date: 2012 / In this work we used an arrangement consisting of Cooper pairs (Cooper Pair Box, CPB) interacting with a nanomechanical Resonator (NR) for various studies: to produce controlable holes in the statistical distribution of excitations of the NR, for resonant and non-resonant cases; to study the evolution of the entropy and the inversion of excitations, including losses in the CPB; and to study the evolution of the Wigner function under the infuence of a reservoir. We have obtained the exact solution of the master equation describing the non-degenerate parametric amplifier interacting with a generalized model of linear phase sensitive reservoir, having the form of the equation equivalent to that of the Fokker-Planck propagator for the Wigner function. We have calculated the Wigner function describing the temporal evolution of a state initially in a superposition of two coherent states, a kind of "Schr?odinger cat", and finally, we have also studied the temporal evolution of the negativity of this function, one of the indicators of nonclassicality of vibrational states of the NR. / Neste trabalho utilizamos um arranjo formado de pares de Cooper (Cooper Pair Box, CPB) interagindo com um Ressoador Nanomecânico (NR), para v?ários estudos: cavar buracos na distribui?ção estatí??stica de excita?ções do Ressoador, nos casos ressonante e não ressonante; estudar a evolu?ção da entropia e da inversão de excita?ção, incluindo perdas no CPB; e estudar a evolu?ção da fun?ção de Wigner sob a influência de reservatório. Obtivemos a solu?ção exata da equa?ção mestra descrevendo o amplificador paramétrico não degenerado interagindo com um modelo generalizado de reservatório linear sensí??vel ?à fase, tendo a forma da equa?ção equivalente ao do propagador de Fokker-Planck para a fun?ção de Wigner. Calculamos ainda a fun?ção de Wigner descrevendo a evolu?ção temporal da superposi?ção de dois estados iniciais coerentes, tipo "gato de Schr?odinger", e finalmente, estudamos detalhes da evolu?ção temporal da negatividade desta fun?ção, um dos parâmetros indicadores de não classicalidade de estados vibracionais do NR.

Arising out of the EPR debate, the Bell and Wigner inequalities of quantum theory are experimentally testable relations which address the question of quantum completeness. This thesis provides feasibility results for a fermionic test of the Bell inequality, and the first known attempt to investigate the completeness question through the Wigner relation. Such a test is made possible by the production of an entangled p-p singlet at the KVI research facility in Groningen, the Netherlands, through the reactions 12C(d,2He)12B and p(d,2He)n. The p-p spin-correlations are analyzable via the KVI's 2-pi polarimeter acceptance, which eliminates loopholes common to previous experiments. The results distinguish between a hidden variables and quantum mechanical description of the universe. Also presented is a critique of the GHZ argument against the existence of local hidden variables.

Arising out of the EPR debate, the Bell and Wigner inequalities of quantum theory are experimentally testable relations which address the question of quantum completeness. This thesis provides feasibility results for a fermionic test of the Bell inequality, and the first known attempt to investigate the completeness question through the Wigner relation. Such a test is made possible by the production of an entangled p-p singlet at the KVI research facility in Groningen, the Netherlands, through the reactions 12C(d,2He)12B and p(d,2He)n. The p-p spin-correlations are analyzable via the KVI's 2-pi polarimeter acceptance, which eliminates loopholes common to previous experiments. The results distinguish between a hidden variables and quantum mechanical description of the universe. Also presented is a critique of the GHZ argument against the existence of local hidden variables.

This work presents a method to quantitatively calculate the error induced through application of approximate boundary conditions in quantum charge transport simulations based on the Wigner transport equation (WTE). Except for the special case of homogeneous material, there exists no methodology for the calculation of exact boundary conditions. Consequently, boundary conditions are customarily approximated by equilibrium or near-equilibrium distributions known to be correct in the classical limit. This practice can, however, exert deleterious impact on the accuracy of numerical calculations and can even lead to unphysical results. The Yoder group has recently developed a series expansion for exact boundary conditions which, when truncated, can be used to calculate boundary conditions of successively greater accuracy through consideration of successively higher order terms, the computational penalty for which is however not to be underestimated. This thesis focuses on the calculation and analysis of the second order term of the series expansion. A method is demonstrated to calculate the term for any general device structure in one spatial dimension. In addition, numerical analysis is undertaken to directly compare the first and second order terms. Finally a method to incorporate the first order term into simulation is formulated.

No description available.

No description available.

Würzburg, Universiẗat, Diss., 2008.

Chemnitz, Techn. Univ., Diss., 2000. / Ersetzt Dokument: http://archiv.tu-chemnitz.de/pub/2000/0087/index.html.

Tese (doutorado)—Universidade de Brasília, Instituto de Física, 2016. / Submitted by Fernanda Percia França (fernandafranca@bce.unb.br) on 2016-12-07T17:15:15Z No. of bitstreams: 1 2016_JoséSilvadaCruzFilho.pdf: 1399057 bytes, checksum: fbb9af5d2a34eb991f05876fa63a4b62 (MD5) / Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2016-12-19T15:09:07Z (GMT) No. of bitstreams: 1 2016_JoséSilvadaCruzFilho.pdf: 1399057 bytes, checksum: fbb9af5d2a34eb991f05876fa63a4b62 (MD5) / Made available in DSpace on 2016-12-19T15:09:07Z (GMT). No. of bitstreams: 1 2016_JoséSilvadaCruzFilho.pdf: 1399057 bytes, checksum: fbb9af5d2a34eb991f05876fa63a4b62 (MD5) / Neste trabalho, utilizamos uma representação da mecânica quântica simplética para estudar teorias de calibre abeliano e não abeliano, bem como soluções da equação de Schrödinger para sistemas caóticos no espaço de fase. No âmbito arcabouço das teorias de calibre, utilizamos as quasi-amplitudes de probabilidade no espaço de fase na análise de transformações do tipo ψ(q,p)→e^(-i˄(q,p) )*ψ(q,p) no contexto dos campos de Dirac , Klein-Gordon e Isospin. No bojo da equação de Schrödinger no espaço de fase, as quasi-amplitudes de probabilidade foram utilizadas no cálculo da função de Wigner para potenciais do tipo Hénon-Heiles. A análise da negatividade da função de Wigner para sistemas caóticos foi realizada mediante uma teoria de perturbação independente do tempo para o caso não degenerado. ________________________________________________________________________________________________ ABSTRACT / In this work, we use a representation of the symplectic quantum mechanics to study abelian and non-abelian gauge theories, and the solutions of the Schrödinger equation for chaotic systems in the phase space. In the framework of gauge theories, we use the quasi-amplitudes of probabilities in the phase space to analyse transformations of ψ(q,p)→e^(-i˄(q,p) )*ψ(q,p) in the context of the Dirac, Klein-Gordon and Isospin fields. In the core of the Schrödinger equation in phase space, the quasi-amplitudes of probability were used in the calculation of the Wigner function for Hénon-Heiles potential-like. The analysis of the negativity of the Wigner function for chaotic systems was carried out by a time-independent perturbation theory for the nondegenerate case.

En physique du solide, l’étude des effets du désordre a mené à la découverte d’une transition de phase. A faible désordre le solide est conducteur. A fort désordre ce dernier devient isolant. Cette dernière porte le nom de “transition d’Anderson” ou encore de “transition métal-isolant”. Elle peut être caractérisée par un exposant critique ν. Il est prédit théoriquement que sa valeur est universelle, autrement dit, qu’elle n’est pas dépendante des détails microscopiques caractérisant le désordre, mais seulement des symétries satisfaites par le hamiltonien. La réalisation expérimentale d’un tel système est délicate. Des effets de décohérence trop nombreux viennent fausser la mesure de l’exposant critique. Pour contourner ces difficultés, nous réalisons un rotateur frappé avec des atomes froids. La dynamique quantique de ce système est connue pour être la même que celle de l’électron dans un potentiel désordonné. Nous testons alors différents jeux de paramètres régissant le désordre microscopique, et montrons que l’exposant critique ν en est indépendant. Ainsi nous prouvons expérimentalement l’universalité de la transition, ainsi que son appartenance à une classe d’universalité : l’ensemble gaussien orthogonal. Nous détaillons par ailleurs un changement de taille dans le dispositif : la réalisation d’une onde stationnaire verticale et d’une détection vélocimétrique par temps de vol. / In solid state physics, the study of the effects of disorder led to the discovery of a phase transition. For weak disorder, the solid is a conductor, whereas for strong disorder it becomes an insulator. This is known as the “Anderson transition” or as the “metal-insulator transition”, and can be characterized by a critical exponent ν. It is theoretically predicted that this exponent’s value is universal, i.e., that it is not determined by the microscopic details, but only by the symmetries of the Hamiltonian.The experimental realization of such a system in condensed matter is rather difficult. Decoherence effects cannot neglected and affect critical exponent’s value. To circumvent this phenomenon, we use cold atoms to experimentally realize a kicked rotor. The quantum dynamics of such a system are known to mimic those of the solid state problem. We hence test different sets of parameters controlling the statistical properties of the disorder, and show that the critical exponent ν is independent. We hereby prove the universality of the transition, and determine experimentally its universality class : the Gaussian Orthogonal Ensemble. We will then detail an important change in the experimental setup : the installation of a vertical standing wave, and of a time-of-flight velocimetric detection.